1. Field of the Invention
The field of the invention relates to ball valves and means and methods for disassembling such valves.
2. Brief Description of the Prior Art
In top-entry, single-body ball valves it is necessary to push back the valve seats in order to remove or insert the ball member of such valves. In certain applications such as coal gasification/liquefaction, the spaces behind the seats become coked or clogged with solids. This makes retraction of the seats difficult when the valve is to be assembled or disassembled.
U.S. Pat. No. 3,891,183 discloses a trunnion-type ball valve having a ball which is rotatable between open and closed positions. A seat and sealing assembly is provided for engagement with a seating surface of the ball. Spring means urge a sealing lip of the sealing assembly towards the ball.
U.S. Pat. No. 4,262,691 discloses a top-entry trunnion ball valve wherein the ball member is provided with cams for moving the seat rings to a retracted position. Separate retainers hold the seat rings in a retracted position while the ball member is removed. A detachable cover plate is provided to permit such removal.
U.S. Pat. Nos. 3,269,692, 3,348,805, 3,501,127, 3,545,721, 3,712,584, 3,893,469 and 4,140,149 disclose various trunnion valves and rotary plug valves which are representative of the present state of the art.